Signs were posted outside the Library of Congress in Washington on Sunday notifying visitors that all Library of Congress buildings would be closed to the public during a government shutdown. (Bill Clark/CQ Roll Call)

It may be hard to believe now, especially for those whose lives were upended the past three days, but this could end up being remembered as the “Never mind” shutdown.

Since the federal government is going to be fully back in business Tuesday — after just one weekday when the lights were only partially and inconsistently turned off — both parties in Congress may have won the same consolation prize for their long weekend of partisan petulance: a get-out-of-political-jail-for-free card.

Probably it is redeemable just this once. The voters won’t so easily accept it again if there’s another impasse when this latest can lands just three weeks down the road, or really at any other time before Election Day — and if it produces lasting furloughs and genuine interruptions in normal federal services.

For now, the deal to hit the pause button is rooted in one of the very few things both parties agree on: The electorate may not have amnesia, but it sure has a short attention span. And that has never been more true than in the Trump era, when news out of Washington with lasting import or alarming consequences has been supplanted time and again, sometimes within a couple of hours, by other news that seems even more momentous or melodramatic.

Working the Weekend: Highlights from the Shutdown Floor Debate

Congressional Democratic leaders are clearly counting on this working in their favor. Otherwise they would not be settling for a temporary agreement that puts them nowhere reliably closer than they were on Friday, when they withheld the Senate votes that would have prevented the shutdown, to their primary goal of the moment: shielding from deportation hundreds of thousands of undocumented immigrants, known as Dreamers, who arrived on the arms of their parents.

The Hill’s Republican bosses are just as surely relying on the super-saturation of the collective American memory. Otherwise they would not have settled on this moment, when they had an opportunity to manifest their competence at the most basic function of governance, to do something very different: use their majority control over both halves of the legislative branch for a continued display of the limits of governing through procrastination, internally driven discord and stiff-arming the other side.

And of course President Donald Trump is assuming this episode will soon be forgotten, or at least won’t reflect on him any worse than anything else he’s touched in the past year. Otherwise he would not have chosen to make this the moment to test-drive a counterintuitive notion: The first person elected president as a decisive business dealmaker is at his most helpful when he remains entirely offstage and miles away as the real compromising gets done.

Who lost?

Polling before the shutdown signaled the president and the congressional GOP had the most to lose from the impasse. In an ABC News-Washington Post survey in the first half of last week, 48 percent put most of the responsibility on them, while 28 percent pegged Hill Democrats for top blame and 18 percent thought the fault should be assigned equally. Respondents to a Morning Consult-Politico poll, which concluded just before the shutdown started, gave the president and congressional Republicans a 5-point edge in culpability.

The reason seems almost self-evident. The winners of the 2016 election campaigned on the promise that coordinated control over all the policymaking branches of government would mean an end to gridlock, so the public was reacting to the prospect of the opposite coming true.

Beyond that, Republicans have been held responsible by the public for all three previous shutdowns of the past quarter century, with their arguments over the size and scope of federal power rejected when the presidents were Democrats Bill Clinton (1995 and 1996) and Barack Obama (2013).

Even so, the GOP marched with a high degree of public unity into last weekend partly because they were emboldened by the Obama shutdown. And Democrats were similarly unified after deriving an altogether different lesson from that 16-day standoff, which happened when the president rejected demands for neutering the Affordable Care Act as the GOP’s price for funding everything else.

For the Republicans, the top takeaway was they could force an unpopular shutdown and then, 13 months later, score a remarkable midterm election victory thanks to the passage of time and the strength of their messaging and legislative tactics over the intervening months. (The party took over control of the Senate and picked up 13 House seats in 2014.)

For the Democrats, the principal lesson was that members could get away with and even benefit from standing up to a president from the other party (especially one with an approval rating way below 50 percent) on a domestic policy dispute vitally important to their political base, even when the dispute is unrelated to the routinized annual fracas over appropriations.

Watch: Schumer: GOP Majority Has 17 Days to Reach Deal on DACA

Short memories

The parallels between now and five years ago have their limits, though, and so both lessons are best taken with some asterisks.

Republicans running for Congress this year have less than 10 months to sell themselves as something other than the party that was in charge during the shutdown.

They are already staring at House and Senate maps that are looking more problematic for them by the week. They have tied themselves, with an uncanny level of outward acceptance, to a highly problematic president with record low approval ratings. And their ability to proactively produce legislative accomplishments this year is close to nonexistent. (Delaying the resolution of last year’s budget to the midpoint of this fiscal year really dims the prospect for an infrastructure package, for one thing.)

And so Republicans will be left to campaign as the party that helped Trump roll back regulations, cut taxes and tip the federal bench to the right in 2017 — but hasn’t been able to get beyond legislative mop-up duties in 2018.

Democrats have the same amount of time to turn their line in the sand on immigration into a political winner, which is hardly a sure thing.

To take the House, and have a shot at the Senate as well, they must win over many thousands of the independents and swing voters furious that their real economic anxieties have gone unaddressed too long by Washington. So Democrats must somehow persuade these working-class voters they will not be forgotten even longer by a party that’s just decided to wager a huge amount of political capital on fixing the plight of young illegal immigrants.

All that, and they still may end up with no bill at all, or only a limited and temporal victory, to show for it.

Finally, both parties are keenly aware that a shutdown lasting not even 72 hours, causing no apparent deaths or really much disruption, may be forgotten by the vast majority of Americans before the Super Bowl, let alone by the time the new authority to obligate appropriated funds next lapses on Feb. 8.

For good or ill, voters may remember any immigration deal for longer. Many will remember if the coming weeks produce a deal on discretionary spending caps that covers the coming year, especially if that paves a way for lawmakers to defy expectations and complete a budget more or less on time for the first time in this millennium.

And, of course, there remain plenty of ways in which the president himself, special counsel Robert S. Mueller III, North Korean leader Kim Jong Un or some other global agitator could unilaterally transform what this year will be about — and make an inconsequential memory out of how the government marked the first anniversary of Trump’s inauguration.